This invention relates to a broadband, lightweight, mechanically flexible antenna having a relatively small electrical length and more specifically relates to such an antenna for receiving television signals.
In the past, there has been considerable difficulty in the antenna art, particularly with respect to the television and amateur broadcast frequencies, in developing a compact, lightweight and easily installed antenna which is adaptable for use indoors as well as outdoors. As an example, an antenna was provided in the form of two matched dipoles which were mounted in a picture frame. This antenna, however, had a highly variable output impedance and low efficiency and, accordingly, was not capable of providing good television reception over the VHF and UHF frequency spectrum.
Subsequently, an approved picture frame antenna was designed wherein a television antenna was mounted on a printed circuit board which was positioned in back of a picture frame. The electrical performance of this antenna, however, was unsatisfactory for receiving signals over the entire UHF and VHF frequency spectrum. Subsequent to this, an antenna was mounted on a printed circuit board, which antenna was basically in the form of a highly modified log periodic antenna which required two channel amplifiers which were mounted directly upon the antenna. The antenna was an improvement over the prior art, since it included a pair of dipoles which were electrically isolated from one another wherein one dipole had a VHF capacitive load while the other dipole had a relatively low frequency inductive load terminated in a capacitive loading. While this antenna could receive signals over the entire UHF and VHF television frequency spectrum, the range of this antenna was not so good.
In addition to antennas specifically developed for television, other antennas have been developed which were capable of being mounted on relatively thin dielectric substrates. As an example, an elongated dipole antenna was formed of a wire construction. This antenna exhibited the characteristics of a single dipole and was not efficient for the reception of television signals unless it was made very long in order to receive the low frequency end of the television frequency spectrum. A multi-dipole antenna was provided which exhibited extremely good electrical characteristics over a bandwidth deviating in the range of 25% from the center frequency thereof. Since this antenna was of a narrow band type, it was not suitable for television reception and in addition would have had to have been inordinately long if utilized to receive the television signals at the lower end of the television spectrum.
It accordingly is an object of this invention to provide a broadband compact flexible antenna having good electrical characteristics over the entire television bandwidth while having a small electrical load.